Little worms eating perennial hibiscus

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joelcoqui Roslyn, United States Jun 06, 2019

Every year worms/catepillars eat my perennial hibiscus so the leaves look like lace. What are these and what is the best way to eradicate them?

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Post #10429815
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Kell San Leandro, CA(Zone 9b) Jun 06, 2019

I would try Bacillus thuringiensis, Bt. It is not a poison so safe to use. The caterpillars have to eat the sprayed leaves to be effective,

I used to have little green ones eat my petunia blooms. 1 spray and they were gone.
https://wimastergardener.org/article/bacillus-thuringiensis-bt/

Post #10429820
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hcmcdole Powder Springs, GA(Zone 7b) Jun 06, 2019

That is probably the insidious Mallow Sawfly. They make lace paper out of my hardy hibiscus and some damage on Rose of Sharon (same family). I wished I had taken action 3 or 4 years ago when I first started noticing them as I believe the longer you wait (years) the worse they become.

I have tried Orchard Spray (pyrethrin and sulfur) with some success but not enough to eliminate them all together. Even tried a little Spinosad which has some control but not enough. Problem is spraying under the leaves and getting the adults for the next wave of attack.

Horrible look but the flowers still bloom nicely and the plant puts out new leaves. GRRR!

Hardy Hibiscus that looks like lace paper, Rose of Sharon that doesn't look much better, and the adult mallow sawfly. GRRR!

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Post #10429823
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Kell San Leandro, CA(Zone 9b) Jun 06, 2019

Well then, forget the Bt. LOL Too bad for that would be a quick fix.
Looks like Hibiscus sawfly larvae as Butch said.
https://davesgarden.com/guides/bf/showimage/6361/#b

I googled it for you.
https://www.emmitsburg.net/gardens/articles/frederick/2005/sawflies.htm
"The University of Maryland, College of Natural Resources recommends the following control: Handpick larvae or prune out affected tissue and destroy. If the population is too big, or the plant is too tall to hand-pick, treat with Conserve."
(https://www.thetreegeek.com/products/conserve/ has Spinosad which Butch used)
"Unfortunately, I took action too late last year and lost one of my dinner plate hibiscus plants. These little sawflies can do a lot of damage in a short time. They are relatively easy to control with foliar sprays, but because the hibiscus sawflies produce up to six generations in one season, the susceptible plants need to be sprayed on numerous occasions."

or
https://www.planetnatural.com/pest-problem-solver/tree-pests/pear-sawfly-control/

All very interesting!

Post #10429847
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joelcoqui Roslyn, United States Jul 16, 2020

Yesss. Isnt it interesting that the flowers still bloom but the leaves are laced.

Post #10493587
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hcmcdole Powder Springs, GA(Zone 7b) Jul 16, 2020

I use Orchard Spray (combo sulfur and pyrethrin these days) for fungus and pests.

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